Here’s a nice photo essay on making a medieval town building.
Corrugated metal roofs are a ubiquitous feature in third world and post-apocalypse game settings. Here’s a nice tutorial on creating them.
The 20th Century Wargames blog has a great photo tutorial on making trench wire
Here’s a brief article on making some small cork tile hills. I like the effect.
Here’s a well thought out method for making an adjustable flight stand.